A telescoping crane can comprise a raisable and lowerable boom formed with a plurality of boom members or sections including an inner telescoping member and at least one other boom member lockable in a plurality of final configurations, and a device for extending the boom members.
The locking of the boom members in their relative extended positions normally is effected manually, e.g. by a lock bolt mounted in a mechanical rod, so that when the crane configuration and the boom length are to be changed, the boom must always be lowered into a horizontal position. Moreover, if a luffing peak or auxiliary arm at the top of the boom is being used it must be demounted. These operations are inconvenient and require considerable expenditure of time and effort.